Tire information detecting device

ABSTRACT

A tire information detecting device includes detecting means for detecting a state quantity in a tire, transmitting means for transmitting a signal outputted from the detecting means, receiving means for receiving the signal transmitted from the transmitting means, the receiving means mounted at a vehicle body side, and a brake actuator adjusted to apply a braking force to the vehicle. The receiving means is positioned at a radially inner side from a major diameter of the brake actuator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119 with respect to a Japanese Patent Application 2003-283537, filed on Jul. 31, 2003, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention generally relates to a tire information detecting device. More particularly, this invention pertains to a tire information detecting device of which receiving unit can reliably receive a signal outputted from a transmitting unit disposed at a disc wheel supporting a tire.

BACKGROUND

Conventionally, a tire information receiving device, which receives a signal outputted from a transmitting unit mounted at a tire wheel without being in contact with the transmitting unit, has been widely known. A type of this tire information receiving device is disclosed in JP9(1997)-240228A2. In this device, one end of a stay member 41 is fixed to a hub 1 at a vehicle side. One end of a stay member 42 is quipped at the other end of the stay member 41. A receiving part 5 is fixed at the other end of the stay member 42. As described above, the receiving part 5 is supported by the cantilevered stators 41 and 42 that are fixed to the vehicle stationary portion. Further, the receiving part 5 is mounted so as to be adjacent to an inner diameter portion of the tire wheel 6.

In a tire information receiving device which receives information of a tire state quantity such as an air pressure outputted from a transmitting part mounted at a disc wheel, recent developments have lead to stabilizing information receiving response and to developing mounting position and method of the receiving device so as to reduce the manufacturing cost.

A need exists for providing a tire information detecting device capable of reliably detecting information such as a tire air pressure.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a tire information detecting device includes detecting means for detecting a state quantity in a tire, transmitting means for transmitting a signal outputted from the detecting means, receiving means for receiving the signal transmitted from the transmitting means, the receiving means mounted at a vehicle body side, and a brake actuator adjusted to apply a braking force to the vehicle. The receiving means is positioned at a radially inner side from a major diameter of the brake actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:

FIG. 1 is a block view illustrating a tire information detecting device applied for a vehicle control system according to an embodiment of the present invention;

FIG. 2 is a view illustrating a receiving unit mounted at a vehicle side according to the embodiment of the present invention;

FIG. 3 is a cross sectional view illustrating a position of the receiving unit of the tire information detecting device mounted in the vicinity of a disc wheel according to the embodiment of the present invention;

FIG. 4 is another cross sectional view illustrating the position of the receiving unit when the disc wheel mounted with the transmitting unit is equipped for a vehicle driven wheel;

FIG. 5A is a view illustrating a conventional structure in which the transmitting unit is fixed at the disc wheel and the receiving unit is fixed at a tire housing side;

FIG. 5B is a characteristic view for explaining a variation of a signal receiving response of the receiving unit fixed at the tire housing side;

FIG. 6A is a view illustrating a structure in which the transmitting unit is fixed at the disc wheel and the receiving unit is mounted at a radially inner side from a major diameter of a brake actuator according to the embodiment of the present invention; and

FIG. 6B is a characteristic view for explaining a variation of a signal receiving response of the receiving unit mounted at the radially inner side from the major diameter of the brake actuator.

DETAILED DESCRIPTION

An embodiment of the present invention will be described hereinbelow in detail with reference to the accompanying drawings.

As illustrated in FIG. 1, a tire information detecting device WIS is provided with a transmitting unit TU (i.e., transmitting means) mounted at or on a disc wheel DW for a driving side vehicle wheel and a receiving unit RU (i.e., receiving means) mounted at a vehicle (main) body side. The transmitting unit TU includes a detecting unit DU (i.e., detecting means) for detecting a tire pressure and a tire temperature, each of which can be a parameter to directly detect a state quantity in a tire T. Therefore, the transmitting unit TU is adjusted to transmit the state quantity detected by the detecting unit DU to the receiving unit RU. The transmitting unit TU further includes a modulating circuit MC (i.e., signal modulating means) for modulating a signal associated with the detected state quantity, and a transmitting antenna TA for actually transmitting the modulated signal to an exterior portion. According to the embodiment of the present invention, the detecting unit DU detects the tire pressure and the tire temperature. However, the detecting unit DU can be added with functions for detecting a vehicle wheel acceleration and for detecting a power supply voltage supplied to the detecting unit DU.

The receiving unit RU includes a receiving antenna RA for receiving a signal transmitted from the transmitting unit TU, a signal demodulating circuit DC (i.e., signal demodulating means) for demodulating the received signal, a vehicle wheel speed sensor SS for detecting a vehicle wheel speed, and a signal processing circuit SMC for feeding the signals from the signal demodulating circuit DC and the vehicle wheel speed sensor SS to a vehicle system control unit VUC. According to the embodiment of the present invention, a widely used signal wire connects the vehicle system control unit VCU with the signal processing circuit SMC, whereby information can be transmitted between the vehicle system control unit VUC and the signal processing circuit SMC.

The transmitting antenna TA of the transmitting unit TU transmits the information such as the tire pressure and the tire temperature to the receiving unit RU at a predetermined time distance. In this case, in order to transmit the information detected by the detecting unit DU to the receiving unit RU, the signal representing the state quantity of the vehicle tire T is modulated by the modulating circuit MC. As non-limiting examples, the information fed from the transmitting antenna TA to the receiving unit RU corresponds to several types of frequencies appropriately set following vehicle types. Each of the frequencies can be 315 MHz, 433 MHz, 868 MHz, or the like. The frequencies to be applied for the tire information detecting device WIS do not have to be limited to the above and can be anything as far as they are defined in a frequency band recognized for each vehicle type.

According to the embodiment of the present invention, communication cycles between the transmitting unit TU and the receiving unit RU are defined independently pursuant to a vehicle stationary condition, a vehicle driving condition, and a vehicle abnormal condition. More particularly, while the vehicle has been under the stationary condition, it is sufficient to perform the communication therebetween only one time for a few hours. However, while the vehicle has been under the abnormal condition, it is preferable to control the communication therebetween to be performed at least once per second. The communication cycle is independently set in response to a condition of a vehicle system. The communication therebetween can be carried on in a manner that the receiving unit RU requests the transmitting unit TU to transmit the signal to the receiving unit RU, in a manner that the transmitting unit TU regularly transmits the signal to the receiving unit RU, or the like. The information (the signal) received by the receiving unit RU is demodulated by the signal demodulating circuit DC and is generated as a signal possessing tens of kilohertz of low frequency. The signal processing circuit SMC digitalizes the signal having the low frequency and transmits the digitalized signal to the vehicle system control unit VCU.

As illustrated in FIG. 1, the receiving unit RU is mounted at the vehicle side according to the embodiment of the present invention. The receiving unit RU is positioned at a radially inner side relative to a major diameter of a brake disc BD (i.e., a brake actuator), i.e., within a range corresponding to a diameter of the brake disc BD. The receiving unit UR is then fixed at a knuckle arm KA (i.e., a linking member) at a vehicle side. The knuckle arm KA is supported by a suspension (not illustrated). According to the embodiment of the present invention, the brake disc BD corresponds to the brake actuator. Alternatively, a drum brake can correspond to the brake actuator.

As illustrated in FIG. 3, the transmitting unit TU having the detecting unit DU is mounted on or near the disc wheel DW. The transmitting unit TU is positioned in a space defined between an outer peripheral surface of the disc wheel DW and the tire T and is fixed to an intermediate position of the disc wheel DW. The intermediate position is defined approximately halfway of an axial dimension of the disc wheel DW extending substantially along a drive shaft DS. The drive shaft DS is connected to an inner hub IH. The brake disc BD is also connected to the inner hub IH. That is, the drive shaft DS, the inner hub IH and the brake disc BD are integrally connected by bolts B. The brake disc BD is jointed to the inner hub IH via the bolts B. Therefore, the disc wheel DW rotates substantially integrally with the drive shaft DS. Further, an outer hub OH is disposed surrounding the inner hub IH. There are plural hub bearings HB disposed between the inner hub IH and the outer hub OH, thereby allowing relative rotation therebetween. The outer hub OH is substantially integrally fixed to the knuckle arm KA. The hub bearings HB do not allow rotational force of the inner hub IH to be transmitted to the outer hub OH.

As described above, the knuckle arm KA is attached with the receiving unit RU. The receiving unit RU includes the transmitting antenna RA, the signal demodulating circuit DC and the vehicle wheel speed sensor SS (i.e., vehicle wheel speed detecting means), all of which are integrally molded with resin. According to the embodiment of the present invention, a sensor with a Hall element is applied as the vehicle wheel speed sensor SS. Therefore, the rotational speed of the disc wheel DW can be obtained by the vehicle wheel speed sensor SS which detects a magnetic field generated in response to rotation of a rotor R. The rotor R is disposed between the inner hub IH and the outer hub OH. According to the embodiment of the present invention, the vehicle speed sensor SS is integrally formed at the receiving unit RU. Therefore, the number of components can be decreased. A manufacturing cost of the receiving unit RU, i.e., a manufacturing cost of the tire information detecting device WIS hence may be able to be effectively reduced. Further, an assembling man-hour may be able to be effectively reduced. Needless to say, the vehicle wheel speed sensor SS can be connected to the receiving unit RU via a connector.

As described above, when the receiving unit RU is mounted at the knuckle arm KA for the vehicle wheel, the receiving unit RU is positioned at the radially inner side from the major diameter of the brake actuator. In this case, the vehicle wheel is driven with a force transmitted from an engine via a transmission.

Next, as illustrated in FIG. 4 showing a vehicle driven wheel receiving no driving force from the engine. When the disc wheel DW mounted with the transmitting unit TU (not shown) is equipped for a vehicle driven wheel, the space for disposing the drive shaft DC is not defined. Therefore, the receiving unit RU is disposed at an area substantially corresponding to a radial directional length of the inner IH, i.e., in the vicinity of the inner hub IH as illustrated in FIG. 4.

Next, following description will be given for describing a variation of a signal receiving response depending upon the mounting positions of the transmitting unit TU and the receiving unit RU with reference to FIGS. 5A, 5B, 6A and 6B.

When the vehicle run, the signal receiving response of the receiving unit RU is explained depending upon each case where the transmitting unit TU is positioned at either A, B, C or D point, with reference to FIGS. 5B and 6B. According to the embodiment of the present invention, the receiving unit RU is positioned inside of the diameter direction of the brake actuator, i.e., in the vicinity of a rotational center of the tire T. Therefore, even if the transmitting unit TU rotates following the rotation of the tire T, a distance between the transmitting unit TU and the receiving unit RU does not vary so that the receiving response can be effectively prevented from fluctuation. That is, a distance between the transmitting unit TU and the receiving unit RU can be maintained at a substantially constant distance value regardless of the rotational position of the transmitting unit TU following the rotation of the tire T. As explained in FIGS. 5B and 6B, a stabilized signal receiving response can be obtained according to the structure illustrated in FIG. 6A.

If the receiving unit TU is not supported at a member such as the knuckle arm KA or the inner hub IH, but is supported by a cantilevered member, the receiving unit TU may be influenced by vibration applied at the cantilevered member. In this case, the receiving response of the receiving unit TU may fluctuate due to the vibration. Further, the cantilevered member may be damaged due to the vibration, wherein a reliability of this receiving device is not assured. Further, a mounting member may be required for fixing the receiving unit TU at the cantilevered member such that the number of components are increased and the assembling hours are also increased.

According to the embodiment of the present invention, the transmitting unit TU and the receiving unit RU are mounted in order to define polarized waves of the units TU and RU approximately in parallel with a rotational shaft of the tire T, respectively. In this case, a polarized area and directional characteristics of the receiving antenna RA can be maintained at a constant value even when the transmitting unit TU rotates, thereby enabling to obtain further preferable signal receiving response.

Further, according to the embodiment of the present invention, a magnetic field component of the wave transmitted from the transmitting unit TU is designed to be approximately in parallel with a rotational shaft of the tire T. Therefore, the polarized area in the responding direction of the receiving antenna RA can be approximately orthogonally oriented relative to the rotational shaft of the tire. That is, the receiving antenna RA is arranged to have the highest precision in sensing the magnetic field component of the wave transmitted from the transmitting unit TU. In this case, the polarized wave area and directional characteristics of the receiving antenna RA can be effectively maintained at a constant value relative to the rotating transmitting unit TU, thereby enabling to obtain further preferable receiving response.

The principles, the preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiment disclosed. Further, the embodiment described herein is to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby. 

1. A tire information detecting device comprising: detecting means for detecting a state quantity in a tire; transmitting means for transmitting a signal outputted from the detecting means; receiving means for receiving the signal transmitted from the transmitting means, the receiving means mounted at a vehicle body side; and a brake actuator adjusted to apply a braking force to the vehicle, wherein the receiving means is positioned at a radially inner side from a major diameter of the brake actuator.
 2. A tire information detecting device according to claim 1, wherein the receiving means is mounted at a linking member supporting a hub.
 3. A tire information detecting device according to claim 1, wherein the transmitting means is mounted at a disc wheel supporting the tire.
 4. A tire information detecting device according to claim 1, wherein the receiving means is provided with vehicle wheel speed detecting means for detecting a vehicle wheel speed.
 5. A tire information detecting device according to claim 1, wherein the brake actuator includes a brake disc, and the receiving means is mounted at a radially inner side from a major diameter of the brake disc.
 6. A tire information detecting device according to claim 1, wherein the brake actuator includes a drum brake, and the receiving means is mounted at a radially inner side from a major diameter of the drum brake.
 7. A tire information detecting device according to claim 1, wherein the detecting means, the transmitting means and the receiving means are mounted at a driven wheel.
 8. A tire information detecting device according to claim 7, wherein the receiving means is disposed at an area substantially corresponding to a radial directional length of the hub.
 9. A tire information detecting device according to claim 1, wherein the detecting means is a detecting unit for detecting an air pressure and an air temperature as the state quantity in the tire, the detecting unit is included in the transmitting means.
 10. A tire information detecting device according to claim 9, wherein the detecting unit detects a vehicle wheel acceleration and a value of voltage supplied to the detecting unit as the state quantity in the tire.
 11. A tire information detecting device according to claim 10, wherein the transmitting means includes signal modulating means for modulating the signal, and the receiving means includes signal demodulating means for demodulating the signal.
 12. A tire information detecting device according to claim 4, wherein the vehicle wheel speed detecting means is integrally formed with the receiving means.
 13. A tire information detecting device according to claim 1, wherein the receiving means is mounted on a linking member at the vehicle body side. 